The purpose of this study is to determine how fasting affects how the body stores sugar within the liver in normal subjects. The results in dog studies showed a nearly two-fold increase in UDP-glucose turnover, as well as a nearly three-fold increase in the amount of UDP-glucose coming through the indirect pathway with two additional days of fasting. The hypothesis to be tested is that in normal volunteers, increased fasting will increase UDP-glucose turnover and the percentage of UDP- glucose turnover coming through the indirect pathway. This study is one in a series of studies that seeks to further our understanding of one aspect of glucose homeostasis, specifically the substrate and hormonal factors which affect the rate of glycogen synthesis in vivo.